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some troubles about ultra current measurement based on AD549

Question asked by Dongyuan on Apr 29, 2014
Latest reply on Apr 30, 2014 by harryh

Recently, I used chipe AD549 to for a I/V converter to amplifier the pA current. But I found the Ibs of AD549 is more than 20pA, which is very different with 50fA that is discribed in its datasheet.  This result I get from NI Multism simulation.

 

So I feel very curious weather there is something wrong in my circuit or AD549 is oringinally not suitable for ultra current amplifer. Looking forward to your kind hlep.

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